On December 22, 1788, Nguyen Hue came to the throne, taking the name of Quang Trung King, and then dispatched the troops to the North to expel the Thanh invader. At noon of the fifth day of the New Year, Quang Trung King and his great army advanced toward Thang Long Citadel, defeating 290,000 Thanh troops, liberating the nation from the domination of the Thanh aggressor. In 1789, Quang Trung opened the first-degree examination in Nghe An, issuing the royal proclamation for learning encouragement to urge localities to re-arrange their studies and examinations and bring Chinese-transcribed Vietnamese language (Chu Nom) to the official status of the nation. However, at the beginning, the way of recruitment was mainly recommendation. During the process of fights, Nguyen Hue paid special attention to gathering the talents and using candor feudal intellectuals. By the end of 1788, when 290,000 Thanh troops attacked our country, Ngo Thi Nham made great contributions to the victory to fight against the invader. After the glorious victory in 1789, Quang Trung King was assigned Ngo Thi Nham to take over the main task in the diplomatic ties with the Thanh Dynasty.
Ngo Thi Nham, with a series of researches on geography, calendar, history and literature comments, political and social comment, administrative documents and diplomatic letters, provided us with many valuable books on the fields of economy, culture, philosophy and diplomatic ties of the last reign of the Le Dynasty and Tay Son.
Scientific researches on the Tay Son Dynasty in Thang Long were also known through many famous names like Phan Huy Ich, Nguyen Huy Luong, Cao Huy Dieu, Ngo Ngoc Du, Ninh Ton, Bui Duong Lich and Nguyen Huu Chinh. In 1792, Quang Trung King passed away. The history of the Tay Son Dynasty was short but left bold features of the nation’s history.